Ignition device



B. c. FISHER 3,016,411

IGNITION DEVICE Jan. 9, 1962 Filed Sept. 8, 1959 INVENTOR. BERNARD C- FTsHER ATTOR NE Y- "United States Patent 3,016,411 IGNITION DEVICE Bernard C. Fisher, Jersey City, N.J., assignor to Neutronic Development Corporation, Englewood, NJ Filed Sept. 8, 1959, Ser. No. 838,681 Claims. (Cl. 123-169) This invention relates to ignition devices used especially with internal combustion engines.

One of the causes of detonation in internal combustion engines is the overheating of parts of the spark plugs, causing them to become incandescent and to take over the firing of the explosive mixture, thus causing firing at the wrong time and consequent detonation and loss of power.

One of the objects of this invention is to provide an ignition device which will operate in such a manner that none of the parts will become incandescent in operation or hot enough to ignite the mixture.

In my United States Patent No; 2,646,782 I have disclosed an ignition device having a cavity or auxiliary firing space therein in which the compressed fuel mixture is stratified according to its air content when compressed and provides a control of the timing of the spark for varying conditions of speed and load, so as to give the maximum firing efiiciency.

It is therefore also one of the objects of the invention to provide an ignition device which combines the control of the firing time by means of the cavity with a greatly increased heat conduction path away from the sparking electrodes for extremely rapid cooling of the electrodes and adjacent parts.

Another object of the invention is to provide an ignition device which requires no gasket when applied to an internal combustion engine, part of the device itself acting in this capacity.

Still another object of the invention is to provide an ignition device for an internal combustion engine in which a relatively long duct of small cross section is provided leading from the atmosphere to a point near the sparking electrodes which admits air to the combustion chamber during the intake stroke and plays an important part in the cooling of the device.

Another object of the invention is to provide an ignition device which will act to scavenge and blow exhaust gases and residues out of vthe combustion area of the engine.

Other objects and advantages will appear as the description proceeds.

The invention is illustrated'in the accompanying drawings, in which:

FIGURE 1 is a sectional elevational view of an ignition device embodying the invention;

FIGURE 2 is fa sectional plan view of the device'taken on the line 2-2 of FIGURE 1;

FIGURE 3 is a bottom view of the device; and

FIGURE 4 is a fragmentary sectional view of a modi- J fied portion of the device.

Referring now to the drawings, the ignition device, which I prefer to call a fuse, comprises a body member 1 which is tubular in form and is preferably made of cold rolled steel. One end 2 is threaded so as to be screwedinto a tapped hole in the engine block3 'of an, 7

internal combustion engine provided with acooling chamber 4 filled with a coolant 5. The other end 6 of the body member is enlarged and has a hexagonal end surface configuration so that a Wrench may be applied thereto in order to screw the fuse into theengine block. A straightcylindrical portion 7 is provided between the threaded end 2 and the enlarged end 6, slightly smaller in diameter than the threaded end and forming a shoulder 3,016,411 Patented Jan. 9, 1962 "ice 8 between it 9 is cut into the shoulder 8 purpose to be described later. The surface of the shoulder 8 between the groove 9 and the portion 2 is cut back so that when the fuse is inserted in an engine the outer rim of the shoulder 8 will engage the engine block.

The body member is provided with two interconnecting bores 10 and 11 having two different diameters. The bore 10 is in the enlarged portion 6 of the body member and has the large diameter, While the bore 11 is in the end 2 and has a smaller diameter. The two bores are joined by a tapered surface 12.

An insulator 13 is fitted Within the body member 1. It has an enlarged portion 14 of sufiicient diameter to fit easily into the bore 10 of the body member and a tapered portion 15 which is small enough in diameter so that its walls are spacedfrom the walls of the bore 11 into which may be greater than the length of the body member. This portion is of smaller diameter than the portion 14 and is tapered slightly from the enlarged portion to which it is joined by a tapered surface 20. The outer end of the portion 19 may be provided with circular corrugations 21 for a short distance from the end to increase the possible electrical path over the outside of the insulator and to provide a greater surface for the radiation of heat.

It is important to make the insulator of some ceramic material having a high heat conductivity, and I have found that brown alumina having a coefficient of thermalconductivity of 0.0180 is satisfactory. h

The insulator is held in the body member 1 by means of a collar nut 22 which engages internal threads provided in the bore 10, a gasket 23, similar to the gasket 18, being provided to make a substantially gas-tight joint. In addition, a ceramic cement may be used between the insulator portion 14 and the body member to increase the sealing eifect.

The insulator has a bore 25 extending coaxially therethrough from the end of the portion 19 to a point near the end ofthe portion 15. This bore is arranged to receive a central conductor 29 which extends through the insulator. The bore 25 terminates a short distance from the end of the portion where itemerges into a second bore 27 somewhat larger in diameter. The conductor 29 terminates at the shoulder formed between the bores 25 and 27. 5

The outer end of the conductor 29 is formed into a terminal stud 32 which has a threaded portion 33 adapted to be screwed into a tapped portion of the outer end of the bore 25 of the insulator, an enlarged flange 34 adapted to fit over the end of the insulator, and a terminal end 35 adapted for making the electrical connection to the device. A gasket 36 of silicone or other suitable material is pr'ovided .underthe flange 3-4, the end of the insulator being recessed to receiveit. i v

A cup-shaped member 30 is insertedinto the bore 27 of the insulatorand forms a lining for the bore, the open end 'of the member extending slightly beyond the end of the insulator. The v.base of ,themember is spot welded 'to theend of the conductor. The outer edge of the member forms the central sparking electrode for the device. In order to, prevent expansion of themember 30 from cracking' the end of the insulator, the member is preferably slotted on diametrically opposite'sides, as at 31, which compensates for unequal expansion under temperature changes. The metal of the member 30 is preferably an alloy of 95% nickel and manganese, although cold rolled steel hasgiven good results.

The spark jumps between the edge of the member 30 and the rim of the shell portion 2 in any radial direction.

The groove 9 forms part of a passageway between the atmosphere and the combustion space of the engine. To this end I provide a duct 43 through the wall of the body member into the groove 9. Between the groove 9 and the combustion space of the engine the passageway comprises the spiral leakage path along the threads of the threaded end 2 of the body member 1.

When the member 1 is screwed into the engine block using a standard uniform thread, one surface of one thread is in contact with one surface of the thread on the other part and there is a slight clearance between the other surfaces of the threads and between the tips of one thread and the valleys of the other. This clearance provides just the right cross section for my purpose. Of course the length of the passageway, thus formed, is an important factor in the amount of gases which will pass through. -I have found that good results are obtained in an ordinary automobile engine if the threaded portion of the end 2 is inch long and threaded with standard 14 millimeter thread with a so-called No. 2 fit having a tolerance of plus or minus 0.002 inch. Different thread dimensions will of course be necessary for different size devices to be used in different size engines.

With the shell described above, no gasket is necessary in screwing the fuse into the engine block, the rim of the shoulder 8 being forced against the surface of the block. Since air is admitted to the groove 9 through the duct 43, a slight leakage at the juncture of the shoulder and the engine block is not objectionable. Under certain conditions, however, I may use a closely fittingsleeve 39 of aluminum or other soft metal which surrounds the shell for a sufiicient distance to cover the duct 43. The sleeve may be provided witha flange 40 which extends between the shoulder 8 and the surface of the engine block and which acts as a gasket, although its principal efiect is to secure the sleeve in position. The walls of the sleeve may be corrugated so as not to interfere with air passing into the duct 43. The sleeve is used principally with engines in which oil is mixed with the gasoline and prevents any spattering of oil from the duct 43.

The end of the portion 2 of the body member is re- 1 duced in diameter for a short distance beyond the threads, and I provide this reduced portion with two diametrically opposite slots 32 extending towards the center and cutting completely through the wall of the portion '2.

The ignition device, when constructed as described above, performs with astonishingefliciency in an internal combustion engine. In the first place, the interior of the cup-shaped 30 and the space between the end of the insulator and the body portion combine to form the cavity referred to in my ,abovermentioned United States Patent No. 2,646,782, which has the eifect of causing Stratification of the air and gas mixture during the compression stroke, producing the blow torch efiect when the spark occurs and controlling the timing of this effect with variations of speed and load.

In the second place, there is a heat conducting path from the member-30 and rod 29 ,Which is far moreetfective than that of any spark plug heretofor used. -The insu lator draws the heat rapidly from themernber 30 and ,rod into its much larger mass from. which the heat passes to the air and through the portion 1410 the body'memberll In the third place, the .air drawn into the groove 9 at high velocity during theintake stroke and through thefhelical path along the threads from the. groove :9 into the' conn the helical path around the threads with great velocity during the exhaust stroke and swirls through the slots 32 and around the space adjacent the sparking electrodes, sweeping all burned gases before it and thoroughly cleaning the sparking electrodes and. the end of the insulator and producing a cooling efliect on these parts. The slots 32 tend to increase the turbulence of air and gases adjacent the electrodes and increase the cooling surface of the end 2 of the body member. Passage of exploding gases through the duct 43 is negligible.

As a result of these effects, the fuse operates relatively cool and neither the end of the insulator nor the sparking electrodes can ever become incandescent and the firing is always under control of the spark regardless of speed or load conditions.

In the embodiment of the invention shown, the following measurements of the important elements have been found to give good results:

Modifications may be made in the parts of the device as shown and described, and I do not wish to limit the invention except as limited by the appended claims.

What I desire to claim and secure by Letters Patent is:

1. An ignition device comprising a tubular -metallic body member having screw threads at one end for attaching said device to an internal combustion engine and having an enlarged other end, an insulator having one end within said body member and the other protruding out of the other end of said body member, said insulator being tapered at said one end, there being a space between the tapered end of said insulator and the interior walls of said body member, a conductor extending through said insulator and having sparking electrode means adjacent the tapered end of said insulator and a connecting terminal extending beyond the other end of said insulator, all but the extreme end of said electrode means being covered by said insulator, said body member having a cavity in the enlarged portion thereof, a duct leading from said cavity to the atmosphere, and means providing a tortuous path of small cross section from said cavity to a point adjacent said electrode means, the length of said path being greater than three times the circumference of said one end of said body member, said one end .of said body member being provided with at least one cut-away portion through the wall thereof near said end, whereby gases can flow through said cutaway portion adjacentsaid electrode means.

2. An ignition device, as definedinclaim l, in which the cut-awayportion throughthe wall of the end of. the body membercomprises a pair of diametrically opposite slotsttransverse to the axisof said body member.

bustion chamber has a very great cooling effect'on the I 3. An ignition device, as defined in claim 2, inwhich the tortuous path between the cavity and the point adjacent the electrode means comprises the'clearance between the threads of the threaded end of the body member and the engine block.

4. An ignition device, as defined in claim 3, in which the insulator .is provided with a recess in the tapered end and the electrode means comprises a cup-shaped member in said recess with the open end thereof protruding from the end of said insulator, said cup-shaped member being in electrical contact with the end of the conductor.

5. An ignition device, as defined in claim 1, in which the insulator is provided with a recess in the tapered end and the electrode means comprises a cup-shaped member in said recess with the open end thereof protruding from the end of said insulator, said cup-shaped member being in electrical contact with the end of the conductor.

References Cited in the file of this patent UNITED STATES PATENTS 1,429,017 Cartmill Sept. 12, 1922 2,646,782 Fisher July 28, 1953 2,708,428 Fisher May 17, 1955 

